fix(physics): delete the query-site broadphase reach filter (#333, closing #337)

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Transition.FindObjCollisionsInCell discarded a shadow candidate when
  |currPos - obj.Position| > sphereRadius + obj.Radius + movement.Length() + 2f

obj.Position is the part ORIGIN; obj.Radius is the physics-BSP ROOT
BOUNDING SPHERE's radius, measured about a centre AP-156 established is
frequently metres from that origin (376 of 973 installed physics-BSP
parts sit further from their part origin than half their own radius,
worst 20.762 m). Geometry deep inside the real bounding sphere was
therefore thrown away before BSPQuery ever ran: solid near the origin,
permeable in a bounded shell beyond it. For the Neftet rock 0xC8766009 /
gfx=0x01004751 the two points are 23.556 m apart, which is #337 — wedged
on the plateau, jumps sinking into the mesh, corpses falling through. A
live capture recorded 7,225 rejections on that one owner, every single
one with wouldAcceptAtCenter=True.

Deleted rather than re-centred. Retail has no distance pre-filter,
disassembled from the PDB-paired v11.4186 binary (CodeView GUID
9e847e2f-777c-4bd9-886c-22256bb87f32) rather than read from Binary Ninja:

  CObjCell::find_obj_collisions @0x0052b750 walks shadow_object_list and
  calls CPhysicsObj::FindObjCollisions (0x0052b78b) UNCONDITIONALLY; its
  only early-out is insert_type == INITIAL_PLACEMENT_INSERT (0x0052b759).
  CPhysicsObj::FindObjCollisions @0x0050f050 contains no float compare at
  all. CPartArray::FindObjCollisions @0x00518180 is a bare do/while over
  parts, and CPhysicsPart::find_obj_collisions @0x0050d8d0 is two null
  checks plus a call. Retail's only spatial rejection is the BSP node
  bounding-sphere test inside the walk — correctly centred, which is
  exactly what the deleted filter was not.

Re-centring it (carry BoundsCenter on ShadowEntry) would have preserved
an invention retail does not have, including a +2f slack and a
movement.Length() term with no retail counterpart, and left a second
reach budget to be tuned forever. Retail's own cross-cell slack constant
is F_EPSILON = 0.0002 m, not 2 m.

The method's comment claimed the filter was "the analog of the part
sorting-sphere early-outs inside retail's CPhysicsObj::FindObjCollisions
— response-neutral, pure perf". Both halves were false and cost #333 and
#337; it is replaced by the disassembly above.

Gate: Issue333BroadphaseReachFilterTests drives the production path
end-to-end (ResolveWithTransition -> FindObjCollisionsInCell ->
CollisionTraversal) on a DAT-free fixture so it runs everywhere, as a
discriminating pair. Sabotage-verified: restore the pre-check and
OffCentreBspFloorStopsAFallingMover reaches z=37.800 — exactly the
unobstructed fall, blockedAtLeastOnce=False — while
CentredBspFloorStopsAFallingMover keeps passing. Without the control a
fixture unable to fall would pass the first test for the wrong reason.

Issue337's skipped TheBroadphaseAdmitsTheSurfaceTheMoverIsStandingOn
asserted the now-deleted predicate and could never have gone green; it
is rewritten as installed-DAT evidence pinning BOTH halves of the
diagnosis and is no longer skipped.

Perf measured, not assumed (Release, synthetic all-BSP cell, per
ResolveWithTransition): at 38 candidates — the live maximum — 10.61 us ->
16.68 us (1.57x); at a deliberately unreachable 200, 17.34 -> 39.48 us
(2.28x); ~0.16 us per additional candidate tested. Over 19,701 live
[reach-q] samples the in-cell count is p50 = 9, p99 = 32, max 38.

The ACDREAM_PROBE_REACH rejectedReach column is kept and is now
structurally 0, so a post-fix capture stays comparable with the pre-fix
one; dropping it would make the two incomparable.

AP-158 retired (110 active AP rows). #333 and #337 closed pending the
user's live acceptance at Neftet.

Solution suite 11,231 passed / 4 skipped / 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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Erik 2026-08-06 22:16:53 +02:00

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